Emerging high-speed communication networks, such as broadband ISDN networks that employ ATM technology, tend to be packet networks rather than circuit-switched networks because the packet structure allows for better resource sharing. In a packet network, sources do not require dedicated bandwidth (e.g., circuits) for the entire duration of a connection. Unfortunately, however, the enhanced flexibility of packet networks also makes it more difficult to effectively control the admission of connections seeking to enter an existing network and to plan the capacity of future networks when they are designed.
The problems of admission control and capacity planning in a packet network may be addressed by a concept known as the "effective bandwidth" or "equivalent bandwidth" of a connection. When employing this concept, an appropriate effective bandwidth is assigned to each connection and each connection is treated as if it required this effective bandwidth throughout the active period of the connection. The feasibility of admitting a given set of connections may then be determined by ensuring that the sum of the effective bandwidths is less than or equal to the total available bandwidth (i.e., the capacity). By using effective bandwidths in this manner, the problems of admission control and capacity planning are addressed in a fashion similar to that employed in circuit-switched networks. Additional details concerning effective bandwidths may be found in U.S. Pat. Nos. 5,289,462 and 5,521,971, for example.
It is often desirable to provide different quality of service (QOS) guarantees to different classes of customers who use a communication network. Network nodes have been designed that partition the connections established on a link into different priority levels, whereby all of the packets queued from connections of a given priority are emitted prior to any packets from connections of a lower priority. Accordingly, allocation of network resources based on different priority levels is becoming a realistic possibility. Known admission control methods which use the effective bandwidth concept, however, assume that the network nodes operate on a First-In-First-Out (FIFO) basis.
It is therefore desirable to employ effective bandwidths for admission control and capacity planning which can account for priorities of service at the network nodes.